1. Field of the Invention
Exemplary embodiments of the present invention generally relate to a lubricant supplying unit, a process unit incorporating the lubricant supplying unit, an image forming apparatus incorporating the lubricant supplying unit, and a method of manufacturing the lubricant supplying unit.
2. Discussion of the Related Art
Full-color image forming apparatuses for electrophotographic image forming, for example, copiers, printers, and facsimile machines, generally perform either a direct transfer operation or an indirect transfer operation. In the direct transfer operation, a toner image formed on an image carrier is transferred directly onto a recording medium that is conveyed along an outer circumferential surface of a sheet conveyance belt. By contrast, in the indirect transfer operation, a toner image is formed on an image carrier that contacts an intermediate transfer belt and is transferred onto an outer circumferential surface of the intermediate transfer belt by an electric field supplied by a transfer bias unit, and is then transferred onto a recording medium conveyed along the outer circumferential surface of the intermediate transfer belt.
After image transfer, residual toner remains on the surface of the image carrier and/or the surface of the intermediate transfer belt. So as not to adversely affect a subsequent image forming operation, a cleaning unit removes the residual toner from the surfaces of the image carrier and the intermediate transfer belt. Known cleaning units typically include a cleaning blade formed by an elastic material such as a rubber material so that the cleaning blade slidably contacts the surface of the image carrier or the intermediate transfer belt to remove the residual toner therefrom.
However, a cleaning member such as the above-described known cleaning blade and a known cleaning brush can wear out with time as they slidably contact the surface of the image carrier or the intermediate transfer belt. The wear of the cleaning blade and the cleaning brush can cause cracks in or deformation thereof, resulting in reduced cleaning ability. In addition, the surface of the image carrier can be worn out as well as due to such contact, thus shortening the life of the image carrier.
To eliminate the above-described wear of the cleaning member and the image carrier, friction resistance between the image carrier and the cleaning member is reduced by supplying lubricant to the surface of the image carrier.
FIG. 1 shows a commonly known lubricant supplying unit that supplies lubricant to the surface of the image carrier.
The lubricant supplying unit shown in FIG. 1 includes a solid lubricant 100, an image carrier 200, a brush roller 300 disposed between the solid lubricant 100 and the image carrier 200, and a spring 400.
The solid lubricant 100 includes a lubricating material such as metal salt of fatty acid and is formed in a stick shape. The brush roller 300 is held in contact with a surface of the image carrier 200 as the spring 400 presses the solid lubricant 100 against the brush roller 300.
The above-described known lubricant supplying unit rotates the brush roller 300 that is pressed against the solid lubricant 100 so as to slidably scrape the solid lubricant 100 and turn the solid lubricant 100 into powder lubricant. The powder lubricant scraped from the solid lubricant 100 adheres to brush fibers of the brush roller 300 and is supplied to the surface of the image carrier 200 as the brush roller 300 rotates.
In a slightly different arrangement shown in FIG. 2, a different known lubricant supplying unit can include a lubricant roller 500. In contract to the stick-shaped solid lubricant of the lubricant supplying unit described below, this known lubricant supplying unit causes the brush roller 300 to rotate and contact the lubricant roller 500 while in rotation, so that the brush roller 300 scrapes the lubricant roller 500 to supply the scraped powder lubricant to the surface of the image carrier 200. Thus, this known lubricant supplying unit employs a roller-shaped lubricant to make the entire circumferential surface a lubricant supplying face, thereby effectively consuming the lubricant.
However, in the related-art lubricant supplying unit shown in FIG. 1, as the brush roller 300 scrapes the solid lubricant 100, as the solid lubricant is consumed it acquires an arc-shaped recess as shown in FIG. 3, forming edge portions E that project sharply from the cut face of the solid lubricant 100. The sharply projecting edge portions E are weak and thus prone to collapse, causing lack or breakage of the solid lubricant 100. Entry of broken-off pieces of solid lubricant into the image forming unit(s) can cause failures related to development, charging, and/or cleaning, resulting in defective images.
One way to counteract the above-described problem is to give the solid lubricant 100 a width B1 greater than an outer diameter “d” of the brush roller 300 as shown in FIG. 4A. By so doing, as shown in FIG. 4B, side portions of widths B2 and B3 at both ends on the cut face of the solid lubricant 100 remain, which can reduce chances of collapse of the solid lubricant 100. However, in this case, an amount of lubricant left unconsumed may increase, which is uneconomical. Further, with such an approach a large space to mount the solid lubricant is required.
Further, as shown in FIG. 2, if lubricant can be formed in a roller shape, the lubricant can be consumed without breakage. However, it is difficult to form lubricant in a roller shape, and moreover, even after a roller-shaped lubricant is made, it is difficult to protect an entire circumferential surface of the roller-shaped lubricant from contamination. In addition, such a roller-shaped lubricant requires a driving mechanism to rotate the roller-shaped lubricant, which can lead to a complicated configuration and a concomitant cost increase.